CONTINUOUS_MODEL CeSupT

ABSTRACT
"Idealized SUPply Terminal for VAV or natural ventilation.

CentralMode > 1E-4
  Massflow is controlled in the range
    (CentralMode*mMin,CentralMode*mMax) by Contr in (0,1).

CentralMode < -0.5
  'Natural ventilation mode'; flow depends linearly on Dp, also when Dp > dp0;
  Massflow = Dp/dp0 * mMax.

CentralMode = 0
  Massflow is set constant, equal to cLow*mMin. Default for cLow = 0.01.

Revisions:

010427 Abg Modified <Rep>: Qn12 replaces Q_R
010228 RSC <Rep> Defined new local variables  Fi12, Q_R

001211 AB  Give M an offset cLow*mMin, when CentralMode > 1e-4.
           Set limit for 'natural vent' to -0.5.

980407 PS  LocalMode removed altogether.

980226 MV  Massflow calc is changed. Now linear behavior will be in use,
           when fan is on, but localmode is still 0.
           cLow is changed to 0.05 to get 0.05 ACH infiltration

980210 PS  Added TSensor link

971204 AB  Introduced CentralMode and LocalMode
  Behaviour is controlled by LocalMode; see below.

    LocalMode = 1
      Set when Dp > dp0; massflow is controlled in the range
      (CentralMode*mMin,CentralMode*mMax) by Contr in (0,1).

    LocalMode = 0
      Set when Dp is below dp0, linear (laminar) flow is assumed and
      massflow varies linearly with Dp in the range (0,mMax).


970604 AB  Added LOC enthalpy HSupt

971001 MV  Contr > -1E-6   is changed to
           Contr > -0.5    to avoid mode change due to 'numerical noise'.
"



EQUATIONS 

   Dp := P1 - P2;


/* massflow equation */
   M =   IF CentralMode > 1e-4 THEN
           (1 - cLow) * CentralMode * (mMax*Contr + mMin*(1 - Contr))
           + cLow * mMin
         ELSE_IF CentralMode < -1e-4 THEN
           Dp/dp0 * mMax
         ELSE
           cLow * mMin
         END_IF
         GOOD_INVERSES(M); 


/* convected heat through terminal */
  HSupt := Enthal(T1, Hum1);

  Q = IF LINEARIZE (1) THEN T1
      ELSE HSupt * M_ass
      END_IF 
  GOOD_INVERSES (Q);


/* fraction transported through terminal */
  Xf = IF LINEARIZE (1) THEN X1
       ELSE X1 * M_ass 
       END_IF 
  GOOD_INVERSES (Xf);


/* moisture transported through terminal */
  Humf = IF LINEARIZE (1) THEN Hum1
         ELSE Hum1 * M_ass 
         END_IF 
  GOOD_INVERSES (Humf);

/*<Rep> +*/
  Qn12 := M * (HSupt - Enthal(T2, Hum2));
  Fi12 := M/RHODRY(T1,Hum1) * 1E+03;
/*<Rep> .*/

  M_ass := M ;

LINKS

  /* type       name           variables... */

  UniAir        inlet          P1, POS_IN M, T1, X1,Hum1 ;

  BiDirAir      zone           P2, POS_OUT M, T2, POS_OUT Q,
                               X2, POS_OUT Xf, Hum2, POS_OUT Humf ;


  ControlLink  control_in      Contr;

  ControlLink  force_control   CentralMode;

  T            TSensor         T1;

  
VARIABLES


/* type       name      role def        min  max   description */

  Pressure    P1        IN   1375      -BIG  BIG   "pressure in"
  Pressure    P2        IN   1325      -BIG  BIG   "pressure out"
  massflow    M         OUT  0.024        0  BIG   "massflow through terminal"
  massflow    M_ass     A_S  0.024        0  BIG   "massflow through terminal"
  Pressure    Dp        LOC    50         0  BIG   "eff pressure diff"

  temp        T1        IN     20  ABS_ZERO  BIG   "temperature in"
  temp        T2        IN     25  ABS_ZERO  BIG   "temperature zone"
  Enthalpy    HSupt     LOC 40000      -BIG  BIG   "enthalpy of supply air"
  HeatFlux    Q         OUT     0.     -BIG  BIG   "heat convected by
                                                    massflow"

  fraction_y  X1        IN    594         0  BIG   "pollutant fractn in"
  fraction_y  X2        IN    594         0  BIG   "pollutant fractn zone"
  FractFlow_y Xf        OUT     0      -BIG  BIG   "pollution transport"


  HumRatio    Hum1      IN   0.006    SMALL  BIG   "moisture fractn in"
  HumRatio    Hum2      IN   0.006    SMALL  BIG   "moisture fractn zone"
  HumFlow     Humf      OUT     0      -BIG  BIG   "moisture transport"

  Control     Contr     IN      0      -BIG    1   "Controller input
                                                     0 -> mMin,
                                                     1 -> mMax"

  Control     CentralMode IN    1        -1  BIG   "Forcing control, =
                                                     >0 local control
                                                      0 low flow
                                                     <0 natural vent"
  HeatFlux     Qn12     LOC     0         -BIG BIG  "HeatFlux out of terminal
                                                      (into zone)"
  VolFlow_m    Fi12     LOC     0         -BIG BIG  "Volume flow out of terminal
                                                      (into zone)"
                                                    
PARAMETERS

/* type        name    role def  min  max  description */

  Pressure     dp0      S_P  5   SMALL BIG "limit for flow control action"
  MassFlow     mMax     S_P .01  SMALL BIG "max requestable massflow"
  MassFlow     mMin     S_P .001 SMALL BIG "min requestable massflow"
  Factor       cLow     S_P .005  0     BIG "massflow when 'off',
                                            i.e. CentralMode = 0"


END_MODEL